1. Field of the Invention
The present invention relates to a stack type heat exchanger, and more particularly to a stack type heat exchanger for use as a vaporizer in the car cooling system and oil cooler, wherein the heat exchanger comprises a plurality of tubular elements including an inner fin member are stacked horizontally or vertically with the interposition of air paths between one tubular element and the next, each of the air paths including an outer fin member.
2. Description of the Prior Art
There is generally known all-purpose stack type heat exchangers which comprise a plurality of tubular elements stacked with the interposition of outer fins between one tubular element and the next, wherein each tubular element comprises a pair of metal plates of thermal conductivity having a tank at least at one end for storing a heat exchange medium. The known heat exchanger of this type are advantageous in that they withstand varying loads applied thereto, and exhibit good performance for its limited capacity.
In order to enhance the efficiency of heat exchange the metal plates are provided with numerous projections and recesses so as to enlarge the effective area for heat transfer (e.g. Japanese Utility Model Laid-Open Specification No. 59-116787). There is another proposal for using a corrugated plate as an inner fin member, which is shown by the reference numeral 100 in FIG. 24.
However it has been found that the uneven surfaces of the metal plates in the first-mentioned proposal is not as effective to increase the area for heat transfer as it is expected, thereby resulting in the limited increase in the efficiency of heat exchange. In the second-mentioned proposal the corrugated plates provide straightforward medium paths, which causes the medium to flow straight. The straightforward flow, though it means a smooth or trouble-free flow, is nevertheless not very effective to increase the effective area for heat exchange.
It is generally appreciated that the inner fins reinforce the tubular elements against a possible compression. However the tubular elements are liable to an elongating stress, particularly when the medium is gasifiable. Under this elongating stress the tubular element tend to become deformed or broken in their joints.